Reppert S M, Weaver D R, Rivkees S A, Stopa E G
Laboratory of Developmental Chronobiology, Boston.
Science. 1988 Oct 7;242(4875):78-81. doi: 10.1126/science.2845576.
In vitro autoradiography with 125I-labeled melatonin was used to examine melatonin binding sites in human hypothalamus. Specific 125I-labeled melatonin binding was localized to the suprachiasmatic nuclei, the site of a putative biological clock, and was not apparent in other hypothalamic regions. Specific 125I-labeled melatonin binding was consistently found in the suprachiasmatic nuclei of hypothalami from adults and fetuses. Densitometric analysis of competition experiments with varying concentrations of melatonin showed monophasic competition curves, with comparable half-maximal inhibition values for the suprachiasmatic nuclei of adults (150 picomolar) and fetuses (110 picomolar). Micromolar concentrations of the melatonin agonist 6-chloromelatonin completely inhibited specific 125I-labeled melatonin binding, whereas the same concentrations of serotonin and norepinephrine caused only a partial reduction in specific binding. The results suggest that putative melatonin receptors are located in a human biological clock.
采用¹²⁵I标记褪黑素的体外放射自显影技术检测人下丘脑的褪黑素结合位点。¹²⁵I标记褪黑素的特异性结合定位于视交叉上核，这是一个假定生物钟的所在部位，而在其他下丘脑区域则不明显。在成人及胎儿下丘脑的视交叉上核中始终能发现¹²⁵I标记褪黑素的特异性结合。对不同浓度褪黑素竞争实验的光密度分析显示为单相竞争曲线，成人（150皮摩尔）和胎儿（110皮摩尔）视交叉上核的半数最大抑制值相当。微摩尔浓度的褪黑素激动剂6-氯褪黑素完全抑制¹²⁵I标记褪黑素的特异性结合，而相同浓度的血清素和去甲肾上腺素仅使特异性结合部分降低。结果表明假定的褪黑素受体位于人类生物钟中。
